1. Field of the invention
The present invention relates to a heat sink for cooling a heat producing element by being mounted on the top face thereof, especially, the present invention relates to the heat sink having a fan assembly attached inside of its body and forcibly cooling a heat producing element with a cooling air generated by the rotation of the fan assembly.
2. Description of the Related Art
Among electronic devices, such as transistors and integrated circuits, it is not necessary for a device consuming a small quantity of current to radiate of heat produced therein, since the amount of heat produced therefrom is small. On the contrary, devices handling a large quantity of current, such as power transistors and integrated circuits for power amplifiers in audio equipment or a current booster in a constant voltage circuit, a large amount of power turns to heat in accordance with the operating state thereof and the device may break down when the temperature of the device increases above the operating temperature.
As a countermeasure to this, a heat sink for cooling the element is mounted on the device producing a large quantity of heat. The heat sink is usually made of a material having a good heat conductivity such as aluminum, and a set of radiating fins are disposed on the upper face of the heat sink. The heat sink is used in circumstances where cooling air is forcibly flowing and is adhered or mounted with pressure on the heat producing element, and the heat produced at the element is transferred to the heat sink and absorbed by its body or dissipated by the flowing air.
However, when the amount of heat produced by the element increases, it is necessary to increase the flowing speed of the cooling air around the element for increasing a cooling efficient, thereby it is required to use a powerful fan. The powerful fan generally requires an increase in the size of the fan or an increase in the rotational speed of the fan, thereby causing an increase in the space for the powerful fan or an increase in the noise generated by the powerful fan, as a result.